Use the A2A (Agent-to-Agent) protocol to send messages, structured data, and files to external agents, inspect their Agent Cards, and track or cancel tasks. Provide the agent's endpoint URL and, when required, an API key. Sim sends that key in X-API-Key for task requests; agents that require a different authentication scheme need a compatible endpoint. Agent Card discovery runs before authentication, so the card must be reachable without that key.
Actions
A2A Send Message
Send a message to an external A2A agent and return its response.
Input
Output
A2A Get Task
Retrieve the current state and result of an A2A task.
Input
Output
A2A Cancel Task
Request cancellation of an in-progress A2A task.
Input
Output
A2A Get Agent Card
Fetch the Agent Card (discovery document) for an external A2A agent.
Input
Output
Task behavior and limits
- A2A Send Message requests blocking execution until the agent reaches a terminal (
completed,failed,canceled,rejected) or interrupted (input-required,auth-required) state. Use A2A Get Task to poll a task you continue later, and branch onstate. - Sim limits each agent HTTP response to 10 MiB, each Agent Card discovery HTTP request to 30 seconds, and task RPC requests to 300 seconds. Discovery tries up to three candidate paths. A blocking request can time out before the remote task completes; use its task ID to check the remote state before retrying.
- Task IDs are scoped to the external agent, not to Sim. Anyone who knows an agent URL and task ID can read or cancel that task unless the agent enforces its own authentication — set an API key for agents that require one.